Generating A Cryptographic Key; Generating A New Firmware Aes Encryption Key; Generating A New Public/Private Ecdsa Pair Of Keys; For Firmware Verification - ST X-CUBE-SBSFU STM32Cube Integration Manual

AN5056
5

Generating a cryptographic key

5.1

Generating a new firmware AES encryption key

Key generation and firmware encryption are performed automatically during the compilation
process with the prebuild.bat and postbuild.bat scripts (Refer to
description of the build process).
Figure 22
same applied to active slot #2 or #3:
1. Change the key value in file OEM_KEY_COMPANY1_keys_AES_xxx.bin
2. Compile SECoreBin: prebuild.bat is executed and se_key.s is generated
3. Compile UserApp: postbuild.bat is executed and UserApp is encrypted
5.2

Generating a new public/private ECDSA pair of keys

for firmware verification

As for the AES encryption key, the public key (SE_ReadKey_Pub()) is automatically
modified when the private key (ECCKEY1.txt) is changed.
Figure 23
cryptography firmware verification of the active slot #1. The same applied for active slot #2
or #3:
1. Change the key value in file ECCKEY1.txt
2. Compile SECoreBin: prebuild.bat is executed and se_key.s is generated
3. Compile UserApp: postbuild.bat is executed and UserApp is encrypted
shows the few steps to modify the firmware encryption key of active slot #1. The

Figure 22. New firmware encryption-key

shows the few steps to modify the private and public keys for ECDSA asymmetric
AN5056 Rev 8
Generating a cryptographic key
[10] for a detailed
27/49
48